1. Field of the Invention
The present invention relates generally to the field of secure transmission of content such as software and movies through public channels. More particularly, the invention relates to receiving encrypted content with a first encryption through a public channel and re-encrypting it for private use with a second encryption.
2. Description of the Related Art
Many different approaches have been taken to prevent unauthorized reproduction and distribution of content such as movies and videos, software and television programming. Most of these approaches have focused on one of two portions of vulnerability of the content. The first portion is the distribution media to the end customer. Cable and satellite broadcasters, for example, broadcast almost all programming with encryption. The keys to the encryption are sent to a set-top box which receives the encrypted broadcast, decrypts it, and forwards it on to playback or recording devices. Similarly, for software distributed over a public channel such as the Internet, the software is frequently encrypted in the transmission between the server and the client, then decrypted upon receipt by the client and installed into the computer in an unencrypted form. In another example, for DVD's (Digital Video Disk or Digital Versatile Disk) there is an encryption format embedded into the disk which is decrypted by the DVD player. The unencrypted signal is then conveyed to playback or recording devices.
All of these systems allow for the transmission channel or media to be secure. Unauthorized users receiving broadcasts of cable or satellite television programs or intercepting communications on the Internet, are frustrated by the encryption that is maintained over the radio or wired link. However in all of these systems, once the signal has been received and decrypted, it is in the clear and freely available for copying, reproduction and distribution.
The second portion of the vulnerability is the use of the content after receipt by the end customer. Several different efforts are aimed at protecting against unauthorized reproduction and distribution of copyrighted content after it has been obtained by a user or consumer. CPRM (Content Protection for Recordable Media) was jointly developed by Toshiba, Intel, IBM and Matsushita to allow consumers to store and replay the extensive range of music content that is becoming available through electronic music distribution platforms. CPRM allows music to be recorded on a portable music player, such as an MP3 player, but prevents the unauthorized reproduction and distribution of the music. HDCP (High-Bandwidth Digital Content Protection) developed by Intel protects digital content as it is transmitted between a set-top box or player to a display or playback or recording device. Like CPRM, HDCP allows a user to enjoy and use the encrypted content, but prevents unauthorized reproduction and distribution. DTCP (Digital Transmission Content Protection) developed by a consortium of hardware manufacturers allows a broadcaster to include a copy control code in any media to control the number and types of copies that can be made to the content. It uses a public key encryption scheme.
In any combination of these systems, the content is decrypted at some point in the distribution chain and at that point becomes vulnerable to unauthorized reproduction and distribution. If the set-top box, which receives the media, is a flexible software driven box such as a personal computer, then the software which performs the decryption as well as the content of the media, may be accessible to users that attempt to produce unauthorized copies. This leaves the content vulnerable, notwithstanding the various efforts that have been applied to encrypt and protect it.